Engine starter



y 1944- 4 J. w. FITZ GERALD 2,348,063

' ENGINE STARTER Filed June is, i942 BMMM Juhz'z MFII'Z Patented May 2, 1944 ENGINE STARTER John W. Fitz Gerald, Milwaukee, Wis, assignor to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Delaware Application June 15, 1942, Serial No. 447,040

Claims.

This invention relates to engine starters and refers particularly to engine starters of the socalled automatic type wherein a pinion is propelled to and from its operative driving position by a screw threaded connection between it and a driven actuator.

One of the problems in starters of this type results from the necessity of providing a stop for limiting the axial movement of the pinion when it reaches its operative driving position. This problem is particularly troublesome in starters for small engines where space is at a premium. In such instances it is not only objectionable but often impossible to use an external stop, that is, one mounted on the drive shaft or the tube which is slipped onto the shaft and secured thereto.

It is therefore an object of this invention to provide a starter so constructed that the pinion stop is inside the hollow screw threaded sleeve by which the pinion is connected to its actuator.

With a view toward attaining maximum simplicity and low production cost, this invention has as another of its objects to provide a novel pinion stop which utilizes the ends of the threads on the actuator as one of the cooperating abutments.

The starter to which this invention is particularly directed is of the type wherein the actuator is drivingly connected with the power shaft through a yieldable coupling which yields resiliently upon the imposition of end thrust thereon produced by the screw action as the load of the engine is picked up.

In this manner the load is gradually applied on the starter motor.

In the past the end thrust reacted against by the yieldable coupling was produced directly by the threaded connection between the actuator and pinion causing the actuator to move back toward the yieldable coupling. With the present construction, however, where forward propulsion of the pinion is arrested by the collision of a stop moving with the pinion against the ends of the actuator threads, such rearward displacement of the actuator is impossible.

It is therefore a further object of this invention to provide a novel manner of translating the engine load into end thrust applied on the yieldabie coupling so that the load can be picked up gradually notwithstanding that the actuator and pinion in effect become one unit when the pinion reaches it fully meshed position.

In this connection it is a more specific object of this invention to provide a coupling member threaded on the actuator to be forced back by screw action during the interval the load of the engine is picked up and the coupling member turns with respect to the actuator to thereby gradually apply torque to the pinion.

-With the above and other objects in View, which Will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partially in side elevation and partially in longitudinal section of a starter embodying this invention and showing the pinion in its retracted inoperative position;

Figure 2 is a view similar to Figure 1 but showing the pinion advanced to its operative driving position; and

Figure 3 is a cross sectional view taken through Figure 2 on the plane of the line 33. I

Referring now more particularly to the accompanying drawing, in which like numerals indicate like parts, the numeral 5 designates the ring gear of an engine to be started, with which a pinion 6 is adapted to be meshed. The pinion 6 is movable axially along and rotarily with a motor driven shaft 1 and is adapted to be automatically propelled into mesh with the ring gear 5 upon initial rotation of the shaft I and to be withdrawn from mesh when the engine starts.

As is customary, such longitudinal propulsion of the pinion is effected by relative rotation between it and an actuator 8. The actuator 8 is a sleeve having two sets of external screw threads 9 and it pitched in the same direction and with an intervening smooth portion Ii.

A hollow shaft or tube 12 fixed as at 3 to the motor shaft i has the actuator sleeve mounted thereon. A spring ring is carried by the tube i2 provides a stop against which the forward end of the actuator abuts to prevent axial movement thereof toward the ring gear.

A resilient or yieldable coupling, indicated generaily by the numeral i5, drivingly connects the actuator with the motor driven shaft i. In the construction illustrated, this coupling consists of an annulus it of rubber or other material having cubical elasticity confined between a driving abuiznent or flange ii and a driven abutment or flange i8. However, any other suitable construction may be employed for the coupling as long as it has endwise resiliency and incorporates a movable member adapted to be moved axially against the resiliency of the coupling.

In the present construction, the driving abutment ii is fixed to the motor shaft and the'tube i2 by the set screw it, but the abutment or flange i8 which is the movable member of the threaded connection between said movable coupling member and the actuator and operable to force said movable coupling member out of its normal position against the resiliency of the coupling during the imposition of the engine load on the starter.

nulus under an initial degree of compression to provide frictional driving engagement between or abutments.

Thus, upon initial operation of the starter,

torque is transmitted yieldingly through the connection I5 to the actuator.

The pinion has an internally screw threaded sleeve 28 extending rearwardly therefrom by which the pinion is mounted on the screw threaded portion 9 of the actuator and by which the pinion is supported for longitudinal motion, it being noted that the, bore inthe pinion has substantial clearance for the shaft 1.

The, screw threaded connection between the pinion and the actuator effects the desired longitudinal propulsion of the pinion upon relative rotation between it and the actuator, but when the pinion reaches its fully meshed position as indicated in Figure 2, a stop abutment 2| carried by the sleeve 20 strikes the end of the threads 9 and prevents further forward propulsion of the pinion with respect to the actuator.

The pinion and actuator thus become in effect one unit whereupon rotation of the actuator ceases until the load of the engine is picked up, and during this interval the threaded connection between the driven abutment or flange I8 and the threads IE] forcesthe abutment or flange l8 back against the resiliency of the coupling. With the gradually increasing resistance the coupling offers to such rearward displacement of the abutment or flange 13 the load of the engine is gradually picked up.

After the starting operation is complete and the pinion is retracted in the customary manner, the resiliency of the coupling restores the abutment I8 to its normal position on the screw threads [0. l V

The stop 2! may take any variety of specific forms but is conveniently obtained by two semicircular ringsslipped intov a counterbore 22 in the open end of the pinion sleeve to be confined between the bottom of the counterbore and a spring retaining ring 23 snapped into a groove in the counterbore.

An anti-creep device 24 of conventional construction guards against accidental movement of the pinion into mesh with the ring gear.

From-the foregoing description, taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the art that this invention provides a starter of novel design and construction and that by virtue of the internal location of its pinion stop it is particularly well adapted for small starters.

What I claim as my invention is:

I. In an engine starter of the type wherein a pinion is automatically propelled axially to and from an operative driving position: a yieldable coupling having axial resiliency and through which the torque to the pinion is transmitted, said coupling including a member movable axially against the resiliency of the coupling; a screw threaded sleeve extending axially from the pinion; a screw threaded actuator restrained against axial motion and having threaded engagement with the pinion sleeve; anda screw 2. In an engine starter: a pinion having an internally threaded sleeve; a screw threaded actuator on which the sleeve is threaded so that relative rotation between the actuator and sleeve effects longitudinal motion of the pinion; cooperating stop abutments on the actuator and sleeve for limiting axial movement of the pinion toward its operative driving position; a stop limiting axial movement of the actuator in the direction the pinion moves toward its operative position; a yieldable coupling for drivingly connecting the actuator with a power source, said coupling including a member movable axially against the resiliency of the coupling; and a screw threaded connection between said axially movable member and the actuator so pitched that relative rotation between said movable member and the actuator occurring during the imposition of the engine load on the starter forces said movable member out of it normal position against the resiliency of the coupling to cushion the application of torque on the engine.

3. In an engine starter: a pinion movable axially to and from an operative driving position; an actuator; a sleeve rigidly connected to the pinion; a threaded connection between the pinion sleeve and actuator operable to propel the pinion axially upon relative rotation between said parts; a yieldable driving coupling for driving the actuator from a power source; cooperating stop abutments on the actuator and pinion sleeve for limiting relative movement therebetween when the pinion is in its operative driving position; and means operable upon cessation of rotation of the actuator as the load of the engine is imposed on the starter for translating the load of the engine into end thrust on the yieldable coupling to thereby cushion the application of the engine load on the starter, said means including a coupling part movable axially relatively to the actuator upon such translation of engine load into end thrust on the coupling.

4. In an engine starter of the type wherein a pinion is automatically propelled to and from an operative position by relative rotation between two screw threadedly connected parts, the combination of an actuator having axially spaced threaded portions the threads of which are pitched in the same direction; a part fixed to the pinion and threaded on one of the screw threaded portions of the actuator; a stop movable with the pinion and along the smooth portion of the actuator between its threaded portions to engage the end of the threaded portion on which the pinion part is threaded and limit axia1 movement of the pinion toward its operative position; and a yieldable drive for the actuator including a part threaded on the other threaded portion of the actuator and a body of elastically deformable material confined between said part and a driving abutment so that the action of the screw threads between said other threaded part and the'actuator tightens the yieldable drive as the load on the starter is picked up. 7

5. In an engine starter: a power driven shaft; a pinion movable coaxially and rotarily with respect thereto; an internally screw threaded sleeve on the pinion; an actuator loose on the shaft and having two axially spaced threaded portions and an intervening smooth portion, one of the threaded portions having the pinion sleeve threaded thereon and the intervening smooth portion being smaller in diameter than said threaded portion so as to provide a stop abutment at the junction of said threaded and smooth portions; a stop movable with the pinion sleeve and along the smooth portion to engage said stop abutment when the pinion reaches its operative position; and a yieldable coupling between the actuator and the power driven shaft including an elastic annulus and a flange abutting said annulus, said flange being threaded on the other screw threaded portion of the actuator to be forced back against the elastic annulus as the load on the starter is picked up.

6. In an engine starter: a power shaft; an externally threaded actuator loose on the shaft but restrained against longitudinal movement in one direction; a yieldable driving connection between the shaft and the actuator comprising an abutment fixed to the shaft, an opposing abutment threaded on the actuator, and an elastic annulus between said abutments and frictionally engaged therewith so that the transmission of torque from the shaft to the actuator depends upon frictional engagement between the abutments and the elastic annulus and between the screw threads on the second abutment and the actuator; a pinion having a threaded connection with the actuator so that relative rotation therebetween propels the pinion longitudinally; and cooperating stop abutments carried by the pinion and the actuator for limiting relative rotation and consequently relative longitudinal motion in one direction between the pinion and actuator so that rotation of the actuator is interrupted during the interval the inertia of the load on the starter is overcome, whereby the abutment threaded on the actuator is forced back against the elastic annulus to tighten the driving connection.

'7. In an engine starter of the type wherein a pinion is automatically propelled to and from an operative driving position by relative rotation between two threadedly connected parts one of which is substantially axially stationary: cooperating stop abutments on said parts for limiting relative movement therebetween when the pinion reaches its operative driving position; a yieldable coupling having endwise resiliency and through which the torque to the pinion is transmitted, said coupling including a member movable axially against the resiliency of the coupling; and a screw threaded connection between said movable coupling member and said substantially axially stationary part for effecting relative rotation between said threaded parts upon initial operation of the starter and operable upon cessation of relative rotation between said parts as the engine load is applied on the starter to effect relative rotation between the movable coupling member and said substantially axially stationary part and consequent displacement of the movable coupling member from its normal position against the resiliency of the coupling until the yielding resistance of the coupling overcomes the engine load.

8. In an engine starter: a pinion member; an actuator; a threaded connection between the pinion member and the actuator operable to move the pinion member axially and to transmit torque thereto; a yieldable coupling for connecting the actuator with a power shaft comprising a driving abutment adapted for securement to the power shaft, a driven abutment and yieldable means spacing the abutments axially from each other; a threaded connection between the actuator and the driven abutment capable of transmitting torque; and stop means engaged by the actuator to prevent relative axial movement between the actuator and the driven abutment upon initial operation of the starter, said threaded connection between the actuator and the driven abutment being so pitched that interference with rotation of the actuator imparted thereto by the driven abutment forces the driven abutment towards the driving abutment against the resiliency of the yieldable means until the yielding resistance of said yieldable means overcomes the load on the actuator restraining its rotation.

9. In an engine starter: a pinion member; an actuator; a threaded connection between the pinion member and the actuator whereby relative rotation therebetween advances the pinion to its operative driving position; stop means for precluding motion of the actuator in the direction of pinion advance; cooperating stop abutments on the pinion member and actuator engageable when the pinion reaches its operative driving position to establish a positive torque transmitting connection in the driving direction and whereby the actuator is restrained against rotary motion until the engine load is overcome; a yieldable coupling for drivingly connecting the act uator with a power source, said coupling having endwise resiliency; cooperating means on the actuator and the coupling rendered operative by the cessation of rotation of the actuator as a result of the imposition of the engine load thereon for translating the engine load into end thrust on the coupling resisted by the endwise resiliency of the coupling which increases with the load to gradually establish a load carrying torque transmitting connection between the actuator and the power source, said coupling means being movable axially relatively to the actuator upon such translation of engine load into end thrust on the coupling.

10. In an engine starter of the type wherein pinion means is automatically propelled to and from mesh with a member of an engine to be started: a rotatable driving member; a rotatable but substantially axially stationary actuating member; a connection between the actuating member and the pinion means through which the pinion means is propelled and driven; a coupling between said members having endwise resiliency; a screw threaded connection between the coupling and one of said members through which torque is transmitted when the threadedly connected parts are restrained against relative endwise motion, relative rotation between the coupling and said member resulting from the restraint against turning imposed on the actuating member by the load of the engine causing the screw threads of said connection to impose an end thrust on the coupling against its yielding resistance which gradually increases until the resistance of the coupling overcomes the engine load whereupon relative rotation at the threaded connection ceases and a load carrying torque transmitting connection is established thereat.

JOHN W. FITZ GERALD. 

